The present invention relates generally to a method of sealing cigarette packages and containers, and more particularly to a method for sealing a cigarette container having an induction heated adhesive bonding a bottom panel to a main body.
Cigarette packages and containers that protect the cigarettes from crushing and/or preserve the freshness of the cigarettes are known in the prior art. Typically, such prior art packages are box-shaped containers made of a paper or cardstock material in either a xe2x80x9csoftpackxe2x80x9d or xe2x80x9chardpackxe2x80x9d form. Softpack packages are capable of retaining a measure of freshness, but softpack packages typically offer little or no protection against crushing. Hardpack packages do help to preserve freshness to some extent and do offer some protection against crushing.
Other materials, such as metals, woods and plastic, have also been suggested for making crushproof and freshness-preserving cigarette containers, but have never attained widespread acceptance because of their typically high manufacturing costs. However, with the advancement of plastic manufacturing technology, it has become more cost effective for cigarette manufacturers to use plastic materials for cigarette containers. U.S. Pat. Nos. 2,867,369 to Cernera and 3,223,275 to Rice, Jr. disclose cigarette containers that may be made out of various materials, such as plastic, wood, metal and cardboard. The use of a plastic container molded from a polymeric material having a relatively low permeability or impermeability would eliminate the need to use wrappers and overwraps or, alternatively, in conjunction with such wrappers and overwraps, the air impermeability of molded plastic containers would be further enhanced.
It would therefore be desirable to be able to provide a cigarette container made of whatever desired material which could be easily and cheaply made.
The present invention is directed to a critical step in the making of a novel cigarette container of any selected material, especially plastic. Although the cigarette container of the invention may be configured in a number of forms that are not specifically illustrated herein, one preferred embodiment of the container comprises a six-sided box which forms a box-shaped container.
According to the method of the present invention for making a cigarette container, a hollow container body is constructed having an open end. The open end includes a step portion defining a surrounding rim and interior abutments. A plug is also prepared which is sized to be received between the rim of the body and to abut the abutments. The plug includes a main plate, a metal layer attached to the main plate, and a heat activated adhesive located adjacent the metal layer and positioned to be immediately adjacent the step portion when the plug is inserted in the open end of the body and the plug contacts the abutments. The main plate is placed in the open end of the body so that the adhesive is disposed between the step portion and the main plate. An induction heating device is then located adjacent the open end of the body, and activated to heat the metal layer and hence to heat the adjacent adhesive so that after cooling the plug is bonded to the body by the adhesive and the plug thus permanently closes the open end of the body.
In one embodiment, the preparing step includes the locating of the adhesive on a top surface of the plate between a border edge of the metal layer and a border edge of the plate. In another embodiment, the preparing step includes the locating of the adhesive on a side edge of the plate below a top surface of the plate either in addition to, or alternatively to, the adhesive on the top surface. In still another embodiment, the preparing step includes the securing of the metal layer to a top surface of the plate, and the locating of the adhesive on a top surface of the metal layer.
In the preferred embodiment, the activating step includes the heating of the metal layer to bring the adhesive to a temperature of less than 200xc2x0 F. This activating step also includes the excitation of the induction heating device at about 1600 Hz.
The disclosed container is preferably made of two components, namely, a body comprising an integral open-ended body and lid, and the flat plug. The flat plug is conveniently die-cut from a flat sheet of a plastic/metal, e.g., a polypropylene/aluminum foil laminate or injection molded of a plastic material, e.g., polypropylene, with a metal foil substrate, such as aluminum foil, bonded to one surface thereof.
The induction heating device for heat-seating the bottom panel to the container body comprises a sealer head made of a non- or low-heat conducting material in which is formed a cavity corresponding in size and geometrical shape to the bottom end of the container. A coil is wound inside the sealer head about the cavity and is energized by electrical energy to generate a magnetic field in the cavity. When a container is positioned in the cavity, the coil is energized to a level that causes the heat-activated adhesive only on the edges of the base in contact with the step portion to be activated.
The induction heating technique described above is preferred because of a number of unique advantages over other techniques. For example, the contacting portions of the base and body may be bonded by other types of adhesives, and/or by ultrasonic or laser welding or other techniques that will be apparent to those of skill in the art. However such techniques are not as quick, easy to control, or available for use in high speed machines as the induction heating technique of the present invention.
Another advantage of the present invention is that the heat induction technique produces little or no out-gassing which may adversely effect the flavor of the adjacent cigarettes. With ultrasonic or laser heating of an adhesive, relatively greater out-gassing is produced.
Still another advantage of the present invention is that when using a heat activated adhesive, it is relatively easy to control the temperature to which the adhesive is heated compared to laser and ultrasonic types of heating.